twinman
Posts: 1628
Joined: 1/19/2002
From: Katy, TX, USA
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Heading Hold Gyros on Airplanes
In the pursuit of excellence and for the glory of the RCU and RC WarBirds Forum, once again we are venturing into areas that sane people would not dare travel.
Some time ago I wrote of numerous experiments with the use and care of gyros. These are detailed in older forums.
I became interested in the helicopter style gyro called "heading hold". (Told you twins make you crazy!!!!)
This is the gyro that allows the fantastic three D maneuvers that we see the copters perform. Many people told me that heading hold gyros were not for airplanes....I really hate to be told that I cannot do something!!! ( See Bull Headed in the Dictionary...my picture is near by!) Bought one of the Futaba 401 gyros, which was highly recommended by the copter guys at the field.
The instructions are really not aimed at the airplane guys, so a bit of on the ground experimentation was in order. ( NOT COMPLETELY CRAZY1)
These gyros are controlled with a two position switch, such as the gear switch. The gain of the gyro in each switch position is controlled by the "travel" ( Sometimes called ATV setting) in each position. More travel, more sensitivity.
Standard Gyro Mode
In one position, the gyro acts like a standard gyro. It resists movement by momentarily moving the rudder in the direction of fuselage deflection, but in neutral position of the control sticks on the transmitter, the rudder will always go back to center.
Heading Hold Gyro Mode
In the other switch position, the rate gyro effect comes into
play...and the world is a very different place!!!
1. The receiver must be turned on with the heading hold switch position selected and left alone for five seconds to orient itself. Turn the switch on the transmitter to normal gyro position before even thinking about taking off!!
2. In the heading hold position of the transmitter switch, the rudder will not "Jump" if the fuselage is moved, it stays in the deflected position. The amount of deflection is in direct proportion to the fuselage movement, ( It stays deflected!) until the fuselage is recentered!!! The rudder is aggressively fighting to push the fuselage back to the original orientation, and will not quit until it gets there. This is an important difference and must be burned into your mind!!!
3. If the rudder stick on the transmitter is moved to a new position, the gyro now tries to hold the rudder in the new position. Yes, you heard right. Stick moved and released, and the rudder stays deflected!!! It does not now go to center. This could be interesting, in the air, if one is not aware of this phenomena. The plane would now try to fly in a permanently held yaw position!!! ( Would be my luck that the engine on the down side of the yaw would pick that time to quit)
4. Turn the heading hold gyro switch to the normal gyro position, and the rudder immediately recenters on the vertical stabilizer.
In Flight Trials
The gyro was installed in my favorite nonwarbird twin, the Twin Long John,on the rudder control, (You really did not think I would risk a twin warbird, did you?!!) which also the most responsive to rudder input.
I set the normal gyro mode to 50% and the same for the heading hold position. If you remember, the rate, or sensitivity, of the gyro is adjustable. Too much, and the plane will "Wag" in the air. Too little and the gyro will not provide the desired assist.
Take off was completely consistent with previous gyro experiences in that it was bullet straight. ( Normal gyro mode)
Remember that you must fly coordinated rudder control with the ailerons in turns or the gyro will fight you in turns. Inputting rudder commands overrides the gyro, in the standard gyro flight. The idea was to fly as normal and use the heading hold gyro setting for hovering assistance.
I flew a few laps to get the feeling of the plane, get my heart rate down, and hopefully bore the ever present peanut gallery who was hoping for a good crash. ( Including my copilot son) The plan was to go vertical and turn the heading hold gyro on as the plane headed up and make absolutely sure I turned it off before trying to fly level...and do not touch the rudder while in heading hold!!!
I wanted to see how effective it is in aiding this lazy pilot who is too lazy to spend the hours to do this on my own. ( Hey, I get points for honesty!!)
That was the plan, however, as usual there are always a few snags.
The heading hold gyro works to hold the plane straight up...or whatever vertical you pick.
Naturally, my first two attempts were "Interesting" (The peanut gallery found it entertaining!)
Here is where it gets interesting. Unless the plane goes straight up, the heading hold gyro will hold it in that angle via the rudder.
It is also very difficult for me to not input rudder control and let the gyro do it's thing. ( Remember me burning the USE THE RUDDER MOTTO?
If rudder input is necessary, you must do it very little and slowl, and remember to bring the rudder back to neutral manually. It will not recenter on it's own by only bringing the stick to neutral. If you input rudder commands, with the gyro in the heading hold setting, the heading hold gyro commands the rudder to now assume the new position and holds the plane in a yaw or whatever you last commanded it to do.
No panic, just turn off the heading hold back to standard gyro setting.
Does it work?..Yes, and much better than a standard gyro for vertical aerobatics. It is however much more complicated for the pilot as the gyro must be constantly turned off and on and I do not recommend it for warbirds!!!.
My vote, if you want to use a gyro on a plane, it is better to stick with the standard gyros verses the heading hold.
Twinman
PS Whew, glad that is over!!
TOLD YOU TWINS MAKE YOU CRAZY!!!
Futaba has a good section on this subject at their website also...just wish they had had it before I tried this!!!!
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